Add Go API for offline punctuation models (#1434)

It is contributed by a community user 
from [our QQ group](https://k2-fsa.github.io/sherpa/social-groups.html#qq).

@@ -1283,7 +1283,7 @@ func (sd *OfflineSpeakerDiarization) SetConfig(config *OfflineSpeakerDiarization
 	c.clustering.num_clusters = C.int(config.Clustering.NumClusters)
 	c.clustering.threshold = C.float(config.Clustering.Threshold)
 
-	SherpaOnnxOfflineSpeakerDiarizationSetConfig(sd.impl, &c)
+	C.SherpaOnnxOfflineSpeakerDiarizationSetConfig(sd.impl, &c)
 }
 
 type OfflineSpeakerDiarizationSegment struct {
@@ -1317,3 +1317,51 @@ func (sd *OfflineSpeakerDiarization) Process(samples []float32) []OfflineSpeaker
 
 	return ans
 }
+
+// ============================================================
+// For punctuation
+// ============================================================
+type OfflinePunctuationModelConfig struct {
+	Ct_transformer string
+	Num_threads    C.int
+	Debug          C.int // true to print debug information of the model
+	Provider       string
+}
+
+type OfflinePunctuationConfig struct {
+	Model OfflinePunctuationModelConfig
+}
+
+type OfflinePunctuation struct {
+	impl *C.struct_SherpaOnnxOfflinePunctuation
+}
+
+func NewOfflinePunctuation(config *OfflinePunctuationConfig) *OfflinePunctuation {
+	cfg := C.struct_SherpaOnnxOfflinePunctuationConfig{}
+	cfg.model.ct_transformer = C.CString(config.Model.Ct_transformer)
+	defer C.free(unsafe.Pointer(cfg.model.ct_transformer))
+
+	cfg.model.num_threads = config.Model.Num_threads
+	cfg.model.debug = config.Model.Debug
+	cfg.model.provider = C.CString(config.Model.Provider)
+	defer C.free(unsafe.Pointer(cfg.model.provider))
+
+	punc := &OfflinePunctuation{}
+	punc.impl = C.SherpaOnnxCreateOfflinePunctuation(&cfg)
+
+	return punc
+}
+
+func DeleteOfflinePunc(punc *OfflinePunctuation) {
+	C.SherpaOnnxDestroyOfflinePunctuation(punc.impl)
+	punc.impl = nil
+}
+
+func (punc *OfflinePunctuation) AddPunct(text string) string {
+	p := C.SherpaOfflinePunctuationAddPunct(punc.impl, C.CString(text))
+	defer C.free(unsafe.Pointer(p))
+
+	text_with_punct := C.GoString(p)
+
+	return text_with_punct
+}