Feb 1, 2018 at 3:04:05pm (UTC) | This is log message
2018-02-01T15:04:05Z | This is log message
I found the next formats in go src: https://github.com/golang/go/blob/master/src/log/log.go#L37 But it seems I couldn't manage to do it by using only those ones..
Two options here:
use log.SetOutput to set a custom writer.
Or use the fmt package instead to just print to stdout or elsewhere - the stdlib log package doesn't do much and it's pretty easy to create your own log package which outputs with custom time format(s) to stdout (or a log file). For example here is such a package in a few lines:
package log
import (
"fmt"
"time"
)
var TimeFormat = "2006-02-01T15:04:05Z"
func Printf(format string, args ...interface{}) {
format = fmt.Sprintf("%s %s", time.Now().Format(TimeFormat), format)
fmt.Printf(format, args...)
}
I'd recommend doing this yourself if you have specific needs, and just output to stdout with fmt.Printf. You don't really need a third party log package.
You can use log.SetOutput(...) with an argument writer that prints entries using your desired format (such as the builtin RFC3999 or one of your choice), for example:
const timeFormat = time.RFC3339
type logWriter struct{}
func (lw *logWriter) Write(bs []byte) (int, error) {
return fmt.Print(time.Now().UTC().Format(timeFormat), " | ", string(bs))
}
func main() {
log.SetFlags(0) // Omit default prefixes.
log.SetOutput(new(logWriter)) // Use our custom writer.
log.Printf("Hello, %s!", "World")
// 2018-09-18T14:50:40Z | Hello, World!
}
You can change the timestamp by using a different format, e.g.:
const timeFormat = "Jan 2, 2006 at 3:04:05pm (UTC)"
// ...
log.Printf("Hello, %s!", "World")
// Sep 18, 2018 at 2:52:26pm (UTC) | Hello, World!
https://play.golang.org/p/hPCn3MflkgQ Here is an answer. You should deal with Writer interface and create new Log by using it