netchan: export before import when testing.

Fixes some race conditions.

R=r
CC=golang-dev
https://golang.org/cl/2456041

src/pkg/netchan/netchan_test.go

@@ -29,9 +29,10 @@ func exportSend(exp *Exporter, n int, t *testing.T) {
 	}()
 }
 
-func exportReceive(exp *Exporter, t *testing.T) {
+func exportReceive(exp *Exporter, t *testing.T, expDone chan bool) {
 	ch := make(chan int)
 	err := exp.Export("exportedRecv", ch, Recv)
+	expDone <- true
 	if err != nil {
 		t.Fatal("exportReceive:", err)
 	}
@@ -108,8 +109,15 @@ func TestExportReceiveImportSend(t *testing.T) {
 	if err != nil {
 		t.Fatal("new importer:", err)
 	}
+	expDone := make(chan bool)
+	done := make(chan bool)
+	go func() {
+		exportReceive(exp, t, expDone)
+		done <- true
+	}()
+	<-expDone
 	importSend(imp, count, t)
-	exportReceive(exp, t)
+	<-done
 }
 
 func TestClosingExportSendImportReceive(t *testing.T) {
@@ -134,8 +142,15 @@ func TestClosingImportSendExportReceive(t *testing.T) {
 	if err != nil {
 		t.Fatal("new importer:", err)
 	}
+	expDone := make(chan bool)
+	done := make(chan bool)
+	go func() {
+		exportReceive(exp, t, expDone)
+		done <- true
+	}()
+	<-expDone
 	importSend(imp, closeCount, t)
-	exportReceive(exp, t)
+	<-done
 }
 
 func TestErrorForIllegalChannel(t *testing.T) {
@@ -188,7 +203,11 @@ func TestExportDrain(t *testing.T) {
 		t.Fatal("new importer:", err)
 	}
 	done := make(chan bool)
-	go exportSend(exp, closeCount, t)
+	go func() {
+		exportSend(exp, closeCount, t)
+		done <- true
+	}()
+	<-done
 	go importReceive(imp, t, done)
 	exp.Drain(0)
 	<-done
@@ -205,8 +224,8 @@ func TestExportSync(t *testing.T) {
 		t.Fatal("new importer:", err)
 	}
 	done := make(chan bool)
-	go importReceive(imp, t, done)
 	exportSend(exp, closeCount, t)
+	go importReceive(imp, t, done)
 	exp.Sync(0)
 	<-done
 }