upgrade deps; rewrite smtp session

vendor/github.com/gogs/chardet/detector.go

@@ -85,11 +85,22 @@ var (
 
 // DetectBest returns the Result with highest Confidence.
 func (d *Detector) DetectBest(b []byte) (r *Result, err error) {
-	var all []Result
-	if all, err = d.DetectAll(b); err == nil {
-		r = &all[0]
+	input := newRecognizerInput(b, d.stripTag)
+	outputChan := make(chan recognizerOutput)
+	for _, r := range d.recognizers {
+		go matchHelper(r, input, outputChan)
 	}
-	return
+	var output Result
+	for i := 0; i < len(d.recognizers); i++ {
+		o := <-outputChan
+		if output.Confidence < o.Confidence {
+			output = Result(o)
+		}
+	}
+	if output.Confidence == 0 {
+		return nil, NotDetectedError
+	}
+	return &output, nil
 }
 
 // DetectAll returns all Results which have non-zero Confidence. The Results are sorted by Confidence in descending order.
@@ -99,7 +110,7 @@ func (d *Detector) DetectAll(b []byte) ([]Result, error) {
 	for _, r := range d.recognizers {
 		go matchHelper(r, input, outputChan)
 	}
-	outputs := make([]recognizerOutput, 0, len(d.recognizers))
+	outputs := make(recognizerOutputs, 0, len(d.recognizers))
 	for i := 0; i < len(d.recognizers); i++ {
 		o := <-outputChan
 		if o.Confidence > 0 {
@@ -110,7 +121,7 @@ func (d *Detector) DetectAll(b []byte) ([]Result, error) {
 		return nil, NotDetectedError
 	}
 
-	sort.Sort(recognizerOutputs(outputs))
+	sort.Sort(outputs)
 	dedupOutputs := make([]Result, 0, len(outputs))
 	foundCharsets := make(map[string]struct{}, len(outputs))
 	for _, o := range outputs {