Existing go logging library all use runtime API to get caller when log file line number, which is expensive (we used to that as well #7). It's possible we parse files and add file line number before compile

i.e. standard log package https://golang.org/src/log/log.go?s=5257:5311#L139

if l.flag&(Lshortfile|Llongfile) != 0 {
		// Release lock while getting caller info - it's expensive.
		l.mu.Unlock()
		var ok bool
		_, file, line, ok = runtime.Caller(calldepth)
		if !ok {
			file = "???"
			line = 0
		}
		l.mu.Lock()
}

• logrus does not have it Log filename and line number sirupsen/logrus#63, promethus guys hack around to do it https://github.com/prometheus/common/blob/master/log/log.go#L234-L244

There are essentially two ways (I can think of ...)

In place update special symbol like __FILE__

use a __FILE__ syntax like in script language (python __file__) or C Marco, and using things like go generate with build flag, user need to explicit specify the special for all the logging call

• go does not (plan to) have it spec: add __FILE__ and __LINE__ macro golang/go#12876

log.DebugFLine("__FILE__", "num %d", len(bugs))

Generate new file with different build flag

• replace logging method with new function and location information

code written by user

// +build !gommon_log_line
package foo

var log = logutil.NewPackageLogger()

func bar() {
  log.DebugFLine("github.com/at15/test/foo.go:10:32", "number of bugs %d", len(bugs))
}

code compiled by go tool

// Code generated by gommon from foo.go DO NOT EDIT.
// +build gommon_log_line

package foo

var log = logutil.NewPackageLogger()

func bar() {
   log.DebugFLine("github.com/at15/test/foo.go:10:32", "number of bugs %d", len(bugs))
}

Ref

• https://github.com/WPH95/gosuger