Let user decide what to do if logger is not in context

README.md

@@ -400,6 +400,29 @@ log.Ctx(ctx).Info().Msg("hello world")
 // Output: {"component":"module","level":"info","message":"hello world"}
 ```
 
+### Use default logger from context
+
+If one try to get logger from context that has not logger within it the default, disabled logger will be returned
+```go
+ctx := context.Background()
+
+log.Ctx(ctx).Info().Msg("hello world")
+
+// No output by default!
+```
+You can easily substitute default logger with your own instance
+```go
+logger := log.With().Str("component", "module").Logger()
+
+zerolog.DefaultLogger = &logger 
+
+ctx := context.Background()
+
+log.Ctx(ctx).Info().Msg("hello world")
+
+// Output: {"component": "module", "level": "info", "message": "hello world"}
+```
+
 ### Set as standard logger output
 
 ```go

ctx.go

@@ -4,11 +4,14 @@ import (
 	"context"
 )
 
-var disabledLogger *Logger
+// DefaultLogger is used if user tries to get Logger from context.Context that has not Logger within it
+// By default it is disabled, meaning it logs nothing at all,
+// but it can be easily substituted by custom instance with different behavior.
+var DefaultLogger *Logger
 
 func init() {
 	l := Nop()
-	disabledLogger = &l
+	DefaultLogger = &l
 }
 
 type ctxKey struct{}
@@ -43,5 +46,5 @@ func Ctx(ctx context.Context) *Logger {
 	if l, ok := ctx.Value(ctxKey{}).(*Logger); ok {
 		return l
 	}
-	return disabledLogger
+	return DefaultLogger
 }

ctx_test.go

@@ -24,7 +24,7 @@ func TestCtx(t *testing.T) {
 	}
 
 	log2 = Ctx(context.Background())
-	if log2 != disabledLogger {
+	if log2 != DefaultLogger || log2.level != Disabled {
 		t.Error("Ctx did not return the expected logger")
 	}
 }
@@ -58,6 +58,14 @@ func TestCtxDisabled(t *testing.T) {
 
 	ctx = dl.WithContext(ctx)
 	if Ctx(ctx) != &dl {
-		t.Error("WithContext did not overide logger with a disabled logger")
+		t.Error("WithContext did not override logger with a disabled logger")
+	}
+}
+
+func TestCtxCustomDefault(t *testing.T) {
+	logger := New(ioutil.Discard).With().Str("custom_field", "custom_value").Logger()
+	DefaultLogger = &logger
+	if Ctx(context.Background()) != &logger {
+		t.Error("default logger has not been substituted")
 	}
 }

log.go

@@ -235,7 +235,7 @@ func (l Logger) With() Context {
 //
 // Use this method with caution. If unsure, prefer the With method.
 func (l *Logger) UpdateContext(update func(c Context) Context) {
-	if l == disabledLogger {
+	if l == DefaultLogger {
 		return
 	}
 	if cap(l.context) == 0 {