Create init method on provider interface

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

@@ -0,0 +1,64 @@
+package appinsights
+
+import "fmt"
+
+type DiagnosticsMessageWriter interface {
+	Write(string)
+	appendListener(*diagnosticsMessageListener)
+}
+
+type diagnosticsMessageWriter struct {
+	listeners []chan string
+}
+
+type DiagnosticsMessageProcessor func(string)
+
+type DiagnosticsMessageListener interface {
+	ProcessMessages(DiagnosticsMessageProcessor)
+}
+
+type diagnosticsMessageListener struct {
+	channel chan string
+}
+
+var diagnosticsWriter *diagnosticsMessageWriter = &diagnosticsMessageWriter{
+	listeners: make([]chan string, 0),
+}
+
+func NewDiagnosticsMessageListener() DiagnosticsMessageListener {
+	listener := &diagnosticsMessageListener{
+		channel: make(chan string),
+	}
+
+	diagnosticsWriter.appendListener(listener)
+
+	return listener
+}
+
+func (writer *diagnosticsMessageWriter) appendListener(listener *diagnosticsMessageListener) {
+	writer.listeners = append(writer.listeners, listener.channel)
+}
+
+func (writer *diagnosticsMessageWriter) Write(message string) {
+	for _, c := range writer.listeners {
+		c <- message
+	}
+}
+
+func (writer *diagnosticsMessageWriter) Printf(message string, args ...interface{}) {
+	// Don't bother with Sprintf if nobody is listening
+	if writer.hasListeners() {
+		writer.Write(fmt.Sprintf(message, args...))
+	}
+}
+
+func (writer *diagnosticsMessageWriter) hasListeners() bool {
+	return len(writer.listeners) > 0
+}
+
+func (listener *diagnosticsMessageListener) ProcessMessages(process DiagnosticsMessageProcessor) {
+	for {
+		message := <-listener.channel
+		process(message)
+	}
+}