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Example

file description
main.go bootstraps HTTP server under http://localhost:8080 with contextual request and error fields logging
middleware.go defines contextual request logging HTTP middleware function
hello.go implements naive /hello endpoint which emits a contextual log
try.go implements /try endpoint that most likely fails and logs error with a field
goroutine.go implements /go endpoint which shows how contextual logging can be used to trace forking multiple goroutines

Step by step guide

  1. Open terminal.
  2. Clone this repository. 
    git clone https://github.com/go-logrusutil/logrusutil.git
  3. Enter this directory in terminal. 
    cd logrusutil/example
  4. Run the application. 
    go run .
    Output: 
    time="2019-11-11T22:33:59.1811608+01:00" level=info msg="server starting" app=example
  5. Open http://localhost:8080/hello in a browser. Output: 
    time="2019-11-11T22:34:05.1865488+01:00" level=info msg="request started" app=example reqID=5577006791947779410
time="2019-11-11T22:34:05.187543+01:00" level=info msg="hello world" app=example foo=bar reqID=5577006791947779410
time="2019-11-11T22:34:05.187543+01:00" level=info msg="request finished" app=example reqID=5577006791947779410
    Notice that all logs emitted from a given request have the same request_id field value.
  6. Read hello.go to see how to make contextual logs.
  7. Open http://localhost:8080/try in a browser 2 times. Output: 
    time="2019-11-11T22:34:08.6542691+01:00" level=info msg="request started" app=example reqID=8674665223082153551
time="2019-11-11T22:34:08.655269+01:00" level=info msg="try succeded" app=example reqID=8674665223082153551
time="2019-11-11T22:34:08.6562676+01:00" level=info msg="request finished" app=example reqID=8674665223082153551
time="2019-11-11T22:34:10.4275334+01:00" level=info msg="request started" app=example reqID=3916589616287113937
time="2019-11-11T22:34:10.4285334+01:00" level=error msg="try failed" app=example error="failed to generate an excelent point" point="{2 1}" reqID=3916589616287113937
time="2019-11-11T22:34:10.42955+01:00" level=info msg="request finished" app=example reqID=3916589616287113937
    Notice that the error log has an additional point field.
  8. Read try.go to see how to wrap error with fields.
  9. Read main.go and middleware.go to see how to setup contextual logging and error fields logging.
  10. Open http://localhost:8080/go in a browser. Output: 
    time="2019-11-11T22:34:12.6953435+01:00" level=info msg="request started" app=example reqID=1443635317331776148
time="2019-11-11T22:34:12.6963432+01:00" level=info msg="new jobID" app=example jobID=1 reqID=1443635317331776148
time="2019-11-11T22:34:12.6973451+01:00" level=info msg="request finished" app=example reqID=1443635317331776148
time="2019-11-11T22:34:12.6973451+01:00" level=info msg="new jobID" app=example jobID=2 parentJobID=1 reqID=1443635317331776148
time="2019-11-11T22:34:12.6973451+01:00" level=info msg="new jobID" app=example jobID=3 parentJobID=1 reqID=1443635317331776148
time="2019-11-11T22:34:13.7329305+01:00" level=info msg="easy job done" app=example jobID=2 reqID=1443635317331776148
time="2019-11-11T22:34:22.7370428+01:00" level=info msg="hard job done" app=example jobID=3 reqID=1443635317331776148
    Notice the jobID and parentJobID log fields.
  11. Read goroutine.go to see how contextual logging can be used to trace goroutines.

Tip: Consider debugging the application for deeper understanding.