gotchas.slide

Gotchas
09 March 2018

Dinesh Kumar
Product Engineer, Gojek

https://github.com/devdinu

@devdineshkumar

* Gotchas
- var x Type // default nil
- nil is the zero value for pointers, interfaces, channels, slices, maps and function types, and it represents an uninitialized state
- slice is a reference (*ptr, len, cap)

* Gotchas
.play -edit ./src/refresh/debugging.go

* Gotchas
- function receivers - will not change values if its non pointer
- iteration of map data is random
- range gives values, for mutation you need to use index

* Weird slicing
    WierdSlice([]int{1, 2, 3, 4, 5}, 2)
.play -edit ./gotchas/slice_mutate.go /^func WierdSlice/,/^}/

* Calling on nil
.play ./gotchas/nil_call.go 


* Addressable
.play -edit ./gotchas/addresseable.go

* Goroutines
- waiting on <-channel will block if there's no sender
- explicitly need to wait for the spawned goroutines (waitGroup / time)
- request with context | goroutine with parent context
- use for { select { case } } and ensure you close goroutine on os.Signal or from a channel or ctx.Done()

* Stack and Heap
- compiler decides whether to allocate in heap or stack, so its fine to return a reference to local variable

* HTTP
- set Timeouts
- close response Body and closing at right place (after no error) ( if not it can result in file descriptor leak)
- err = io.Copy(ioutil.Discard, resp.Body)
- req.Close
- recover

* References:
 - http://devs.cloudimmunity.com/gotchas-and-common-mistakes-in-go-golang
 - https://medium.com/golangspec/detect-locks-passed-by-value-in-go-efb4ac9a3f2b

* License
.image ./images/by-sa.png