Go 1.20 new features

Quick review of Go 1.20 features

• Go 1.20 new features
  • Profile Guided Optimization
    • Merging different profiles
  • Integration test coverage
  • Array to slice conversion
  • New errors wrapping

Profile Guided Optimization

Profile guided optimization is used to generate more optimized code from using CPU profiles from captured running system.

1. Add profiling to your program defer profile.Start(profile.CPUProfile, profile.ProfilePath(".")).Stop()
2. Build your program as usual
3. Run your program with under load
4. Build your program with flag -pgo <path/to/profile>
5. Enjoy

Merging different profiles

You can run profiling of your code multiple times. Then you should merge your profiles go tool pprof -proto a.pprof b.pprof > merged.pprof

Integration test coverage

Now you can check coverage of integration tests of go programs. To try this just do following steps:

1. Build program with coverage flag go build -cover ...
2. Run program with set env GOCOVERDIR
3. Optionally merge results go tool covdata merge -i=<directories> -o merged

Array to slice conversion

You can now convert arrays to

s := make([]byte, 2, 4)
a0 := [0]byte(s)
a1 := [1]byte(s[1:]) // a1[0] == s[1]

New errors wrapping

Errors now can wrap multiple errors

err1 := fmt.Errorf("first sample error")
err2 := fmt.Errorf("second sample error")
err3 := fmt.Errorf("third sample error")

complexErr1 := fmt.Errorf("first complex error %w, %w", err1, err2)
complexErr2 := fmt.Errorf("first complex error %w, %w", complexErr1, err3)