Handle concurrency in tests and logger

- Live Share tests
- Logger implementation for ghcs

cmd/ghcs/output/logger.go

@@ -3,6 +3,7 @@ package output
 import (
 	"fmt"
 	"io"
+	"sync"
 )
 
 // NewLogger returns a Logger that will write to the given stdout/stderr writers.
@@ -19,6 +20,7 @@ func NewLogger(stdout, stderr io.Writer, disabled bool) *Logger {
 // If not enabled, Print functions will noop but Error functions will continue
 // to write to the stderr writer.
 type Logger struct {
+	mu      sync.Mutex // guards the writers
 	out     io.Writer
 	errout  io.Writer
 	enabled bool
@@ -29,6 +31,9 @@ func (l *Logger) Print(v ...interface{}) (int, error) {
 	if !l.enabled {
 		return 0, nil
 	}
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
 	return fmt.Fprint(l.out, v...)
 }
 
@@ -37,6 +42,9 @@ func (l *Logger) Println(v ...interface{}) (int, error) {
 	if !l.enabled {
 		return 0, nil
 	}
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
 	return fmt.Fprintln(l.out, v...)
 }
 
@@ -45,15 +53,22 @@ func (l *Logger) Printf(f string, v ...interface{}) (int, error) {
 	if !l.enabled {
 		return 0, nil
 	}
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
 	return fmt.Fprintf(l.out, f, v...)
 }
 
 // Errorf writes the formatted arguments to the stderr writer.
 func (l *Logger) Errorf(f string, v ...interface{}) (int, error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
 	return fmt.Fprintf(l.errout, f, v...)
 }
 
 // Errorln writes the arguments to the stderr writer with a newline at the end.
 func (l *Logger) Errorln(v ...interface{}) (int, error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
 	return fmt.Fprintln(l.errout, v...)
 }