add source with func name

source.go

@@ -0,0 +1,45 @@
+package log
+
+import (
+	"context"
+	"fmt"
+	"path/filepath"
+	"runtime"
+
+	"gitoa.ru/go-4devs/log/entry"
+	"gitoa.ru/go-4devs/log/field"
+)
+
+func WithSource(depth int) Middleware {
+	const offset = 3
+
+	return func(ctx context.Context, data *entry.Entry, handler Logger) (int, error) {
+		pc, file, line, has := runtime.Caller(depth + offset)
+		if !has {
+			return handler(ctx, data.AddAny(KeyLevel, field.NilValue()))
+		}
+
+		fnc := runtime.FuncForPC(pc)
+
+		return handler(ctx, data.AddAny(KeySource, Source{
+			Func: filepath.Base(fnc.Name()),
+			File: filepath.Base(file),
+			Line: line,
+		}))
+	}
+}
+
+// Source describes the location of a line of source code.
+type Source struct {
+	Func string `json:"func"`
+	File string `json:"file"`
+	Line int    `json:"line"`
+}
+
+func (l Source) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("%s:%d", l.File, l.Line)), nil
+}
+
+func (l Source) MarshalJSON() ([]byte, error) {
+	return fmt.Appendf([]byte{}, `{"file":"%s","line":%d,"func":"%s"}`, l.File, l.Line, l.Func), nil
+}