Update Go documentation to use NewClient instead of Dial (#1295)

content/en/blog/a-short-introduction-to-channelz.md

@@ -96,9 +96,8 @@ As the error is on the client side, let's first click on
 TopChannels is a collection of root channels which don't have parents. In
 gRPC-Go, a top channel is a
 [ClientConn](https://godoc.org/google.golang.org/grpc#ClientConn) created by the
-user through [Dial](https://godoc.org/google.golang.org/grpc#Dial) or
-[DialContext](https://godoc.org/google.golang.org/grpc#DialContext), and used
-for making RPC calls. Top channels are of
+user through [NewClient](https://godoc.org/google.golang.org/grpc#NewClient),
+and used for making RPC calls. Top channels are of
 [Channel](https://github.com/grpc/grpc-proto/blob/9b13d199cc0d4703c7ea26c9c330ba695866eb23/grpc/channelz/v1/channelz.proto#L37)
 type in channelz, which is an abstraction of a connection that an RPC can be
 issued to.

content/en/docs/languages/go/alts.md

@@ -15,7 +15,7 @@ code:
     )
 
     altsTC := alts.NewClientCreds(alts.DefaultClientOptions())
-    conn, err := grpc.Dial(serverAddr, grpc.WithTransportCredentials(altsTC))
+    conn, err := grpc.NewClient(serverAddr, grpc.WithTransportCredentials(altsTC))
     ```
   server_credentials: |
     ```go
@@ -37,7 +37,7 @@ code:
     clientOpts := alts.DefaultClientOptions()
     clientOpts.TargetServiceAccounts = []string{expectedServerSA}
     altsTC := alts.NewClientCreds(clientOpts)
-    conn, err := grpc.Dial(serverAddr, grpc.WithTransportCredentials(altsTC))
+    conn, err := grpc.NewClient(serverAddr, grpc.WithTransportCredentials(altsTC))
     ```
   client_authorization: |
     ```go

content/en/docs/languages/go/basics.md

@@ -389,12 +389,12 @@ service. You can see our complete example client code in
 
 To call service methods, we first need to create a gRPC *channel* to communicate
 with the server. We create this by passing the server address and port number to
-`grpc.Dial()` as follows:
+`grpc.NewClient()` as follows:
 
 ```go
 var opts []grpc.DialOption
 ...
-conn, err := grpc.Dial(*serverAddr, opts...)
+conn, err := grpc.NewClient(*serverAddr, opts...)
 if err != nil {
   ...
 }
@@ -402,8 +402,8 @@ defer conn.Close()
 ```
 
 You can use `DialOptions` to set the auth credentials (for example, TLS, GCE
-credentials, or JWT credentials) in `grpc.Dial` when a service requires them.
-The `RouteGuide` service doesn't require any credentials.
+credentials, or JWT credentials) in `grpc.NewClient` when a service requires
+them. The `RouteGuide` service doesn't require any credentials.
 
 Once the gRPC *channel* is setup, we need a client *stub* to perform RPCs. We
 get it using the `NewRouteGuideClient` method provided by the `pb` package