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David Eisinger
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static/archive/stephenn-com-kbiijs.txt
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static/archive/stephenn-com-kbiijs.txt
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[1]Stephen's Tech Blog
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* [2]Webhook Wizard 🧙♂️
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Gopher Wrangling. Effective error handling in Go
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June 19, 2023 · 4 min · Stephen Nancekivell
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Table of Contents
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* [3]Guiding principle
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[4]1. Always handle errors
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[5]2. Log errors in one layer
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[6]3. Returning async errors
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[7]4. Wrapping errors
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[8]5. Downgrade errors Warnings
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When programming in Go, the amount of error handling is something that
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slaps you in the face. Most API’s you deal with will expose errors. It
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can become overwhelming, but with a few tips and a guiding principle we
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can make handling errors easy, keep our code clean and give you the
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confidence that nothing is breaking in production.
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A cartoon of a crazy stressed programmer pulling their hair out in
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front of lots of screens showing a error exclamation marks
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A cartoon of a crazy stressed programmer pulling their hair out in
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front of lots of screens showing a error exclamation marks
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Guiding principle[9]#
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The goal for our error handling strategy is that it should require
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minimal effort and provide an easy way to debug any errors that do
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occur.
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We wont cover strategies like retrying because they are less common and
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also expose errors.
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1. Always handle errors[10]#
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Always handle errors. Sometimes it’s tempting to skip one, you might
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not expect that error to ever happen. But that’s why it’s an exception!
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You need to handle it so that you can find out clearly if it ever does
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happen.
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If you don’t handle the error, the expected value will be something
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else and just lead to another error that will be harder to debug, or
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worse it could lead to data corruption.
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In most cases to handle the error all you need to do is return it to
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the caller of your method, where they can log it.
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For example, when refreshing some data you might load it, then save it.
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If you skip the error handling it could overwrite potentially useful
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data with corrupt data.
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👎 Bad error handling
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func refresh() {
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bytes, _ := loadData()
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saveData(bytes)
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}
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👍 Good error handling
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func refresh() error {
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bytes, err := loadData()
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if err != nil {
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return err
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}
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saveData(bytes)
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}
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2. Log errors in one layer[11]#
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You always want to log your errors, ideally to something that will
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notify you about the error, so you can fix it. There is no point
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logging the error multiple times at every layer. Make it the top
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layer’s responsibility and don’t log in any services or lower level
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code.
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Make sure your logging framework is including stack traces so you can
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trace the error to its cause.
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For example in a web app you would log the error in the http handler
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when returning the Internal Server status code.
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👍 Good error handling
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func refresh() error {
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bytes, err := loadData()
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if err != nil {
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return err
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}
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saveData(bytes)
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}
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func (h *handlers) handleRefreshRequest(w http.ResponseWriter, r *http.Request)
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{
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err := refresh()
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if err != nil {
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log.Error("unexpected error processing request %w", err)
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w.WriteHeader(http.StatusInternalServerError)
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return
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}
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w.WriteHeader(http.StatusOK)
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}
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3. Returning async errors[12]#
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When processing data concurrently using a go-func’s, it can be annoying
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to return the error. But if you don’t your app will be less
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maintainable. To handle async errors, return them via a channel to the
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calling thread.
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👎 Bad error handling
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func refreshManyConcurrently() {
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go func(){
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refresh(1)
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}()
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go func(){
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refresh(2)
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}()
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}
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👍 Good error handling
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func refreshManyConcurrently() error {
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errors := make(chan error, 2)
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go func(){
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errors <- refresh(1)
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}()
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go func(){
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errors <- refresh(2)
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}()
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return multierror.Combine(<-errors, <- errors)
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}
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When calling functions that return a value and a possible error using a
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type like Result[T], to wrap the response to pass on the channel.
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type Result[T any] struct {
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Value T
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Error error
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}
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4. Wrapping errors[13]#
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Sometimes you want to add additional context to an error message. Eg to
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include the id of the request that caused the error. You can use
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fmt.error for this.
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err := saveToDb(user)
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if err != nil {
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return fmt.errorf("unexpected error saving user. userId=%v error=%w", user.I
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d, err)
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}
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Usually this isn’t necessary and its better to just return the error
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unwrapped.
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5. Downgrade errors Warnings[14]#
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There are types of errors that regularly occur during normal operation.
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The system might not be able to prevent them all the time, but they
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don’t need to investigate every time. It is better to treat them as
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warnings rather than errors. These might be for things like timeouts or
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intermittent connection errors.
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👍 Good error handling
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func (h *handlers) handleRefreshRequest(w http.ResponseWriter, r *http.Request)
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{
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err := refresh()
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if err != nil {
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if err == context.DeadlineExceeded {
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log.Warn("Timeout error processing request %w", err)
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} else {
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log.Error("unexpected error processing request %w", err)
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}
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w.WriteHeader(http.StatusInternalServerError)
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return
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}
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w.WriteHeader(http.StatusOK)
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}
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[15]Next »
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How to Serve Web Sockets with Http4s
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© 2023 [16]Stephen's Tech Blog
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References
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Visible links:
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1. https://stephenn.com/
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2. https://webhookwizard.com/
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3. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#guiding-principle
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4. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#1-always-handle-errors
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5. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#2-log-errors-in-one-layer
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6. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#3-returning-async-errors
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7. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#4-wrapping-errors
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8. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#5-downgrade-errors-warnings
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9. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#guiding-principle
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10. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#1-always-handle-errors
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11. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#2-log-errors-in-one-layer
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12. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#3-returning-async-errors
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13. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#4-wrapping-errors
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14. file:///var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#5-downgrade-errors-warnings
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15. https://stephenn.com/2022/07/web-sockets-with-http4s/
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16. https://stephenn.com/
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Hidden links:
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18. https://twitter.com/intent/tweet/?text=Gopher%20Wrangling.%20Effective%20error%20handling%20in%20Go&url=https%3a%2f%2fstephenn.com%2f2023%2f06%2fgopher-wrangling.-effective-error-handling-in-go%2f&hashtags=
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19. https://www.linkedin.com/shareArticle?mini=true&url=https%3a%2f%2fstephenn.com%2f2023%2f06%2fgopher-wrangling.-effective-error-handling-in-go%2f&title=Gopher%20Wrangling.%20Effective%20error%20handling%20in%20Go&summary=Gopher%20Wrangling.%20Effective%20error%20handling%20in%20Go&source=https%3a%2f%2fstephenn.com%2f2023%2f06%2fgopher-wrangling.-effective-error-handling-in-go%2f
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20. https://reddit.com/submit?url=https%3a%2f%2fstephenn.com%2f2023%2f06%2fgopher-wrangling.-effective-error-handling-in-go%2f&title=Gopher%20Wrangling.%20Effective%20error%20handling%20in%20Go
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23. https://telegram.me/share/url?text=Gopher%20Wrangling.%20Effective%20error%20handling%20in%20Go&url=https%3a%2f%2fstephenn.com%2f2023%2f06%2fgopher-wrangling.-effective-error-handling-in-go%2f
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24. file://localhost/var/folders/q9/qlz2w5251kzdfgn0np7z2s4c0000gn/T/L18069-7455TMP.html#top
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25. https://github.com/stephennancekivell
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26. https://twitter.com/hi_stephen_n
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27. https://www.linkedin.com/in/stephen-nancekivell-77003039
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28. https://stackoverflow.com/users/893854/stephen
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