add default logger, support parse environment variables automatically.

go.mod

@@ -1 +1,3 @@
 module github.com/cosiner/go-di
+
+go 1.4

inject.go

@@ -4,6 +4,7 @@ package di
 import (
 	"errors"
 	"fmt"
+	"os"
 	"reflect"
 	"regexp"
 	"sync"
@@ -36,6 +37,18 @@ func New() *Injector {
 	}
 }
 
+func NewAndParseEnv(prefix string) *Injector {
+	inj := New()
+
+	if os.Getenv(prefix+"DI_SYNC") == "true" {
+		inj.UseRunner(syncRunner{})
+	}
+	if os.Getenv(prefix+"DI_LOG") == "true" {
+		inj.UseLogger(DefaultLogger{})
+	}
+	return inj
+}
+
 func (j *Injector) UseRunner(r Runner) *Injector {
 	j.runner = r
 	return j

plugin.go

@@ -2,6 +2,7 @@ package di
 
 import (
 	"fmt"
+	"log"
 	"runtime"
 	"sync"
 	"time"
@@ -11,6 +12,7 @@ type Logger interface {
 	Begin(name string, at time.Time)
 	End(name string, at time.Time, dur time.Duration)
 }
+
 type nopLogger struct{}
 
 func (nopLogger) Begin(name string, at time.Time)                  {}
@@ -145,3 +147,13 @@ func (a *asyncRunner) waitDone() error {
 	a.mu.Unlock()
 	return err
 }
+
+type DefaultLogger struct{}
+
+func (DefaultLogger) Begin(name string, at time.Time) {
+	log.Printf("Begin %s\n", name)
+}
+
+func (DefaultLogger) End(name string, at time.Time, dur time.Duration) {
+	log.Printf("End %s - %s\n", name, dur)
+}