logger: initialise L to a no-op SugaredLogger by default

Production code calls Init() from main, but tests and any other entry
point that imports the logger package without initialising it would
hit a nil-pointer panic on the first L.Warnf / L.Infow call. Default
to zap.NewNop().Sugar() so the global is always safe; Init() still
replaces it with the configured logger.

Author: Datanoise

logger/logger.go

@@ -7,7 +7,10 @@ import (
 	"go.uber.org/zap/zapcore"
 )
 
-var L *zap.SugaredLogger
+// L is the global sugared logger. It is initialised to a no-op so that any
+// code path which calls into it before Init() (notably unit tests) does not
+// nil-panic. Init() replaces it with the configured logger.
+var L = zap.NewNop().Sugar()
 
 func Init(level string, jsonFormat bool, logFile string) (*zap.Logger, error) {
 	var zapLevel zapcore.Level