Create init method on provider interface

vendor/github.com/Microsoft/ApplicationInsights-Go/appinsights/jsonserializer.go

@@ -0,0 +1,45 @@
+package appinsights
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"time"
+)
+
+func (items TelemetryBufferItems) serialize() []byte {
+	var result bytes.Buffer
+	encoder := json.NewEncoder(&result)
+
+	for _, item := range items {
+		end := result.Len()
+		if err := encoder.Encode(prepare(item)); err != nil {
+			diagnosticsWriter.Write(fmt.Sprintf("Telemetry item failed to serialize: %s", err.Error()))
+			result.Truncate(end)
+		}
+	}
+
+	return result.Bytes()
+}
+
+func prepare(item Telemetry) *envelope {
+	data := &data{
+		BaseType: item.baseTypeName() + "Data",
+		BaseData: item.baseData(),
+	}
+
+	context := item.Context()
+
+	envelope := &envelope{
+		Name: "Microsoft.ApplicationInsights." + item.baseTypeName(),
+		Time: item.Timestamp().Format(time.RFC3339),
+		IKey: context.InstrumentationKey(),
+		Data: data,
+	}
+
+	if tcontext, ok := context.(*telemetryContext); ok {
+		envelope.Tags = tcontext.tags
+	}
+
+	return envelope
+}