chore: Upgrade to Go 1.19 (#3617)

This is required as part of #3505.

cli/server.go

@@ -475,8 +475,9 @@ func server() *cobra.Command {
 			server := &http.Server{
 				// These errors are typically noise like "TLS: EOF". Vault does similar:
 				// https://github.com/hashicorp/vault/blob/e2490059d0711635e529a4efcbaa1b26998d6e1c/command/server.go#L2714
-				ErrorLog: log.New(io.Discard, "", 0),
-				Handler:  coderAPI.Handler,
+				ErrorLog:          log.New(io.Discard, "", 0),
+				Handler:           coderAPI.Handler,
+				ReadHeaderTimeout: time.Minute,
 				BaseContext: func(_ net.Listener) context.Context {
 					return shutdownConnsCtx
 				},
@@ -1080,7 +1081,11 @@ func configureGithubOAuth2(accessURL *url.URL, clientID, clientSecret string, al
 func serveHandler(ctx context.Context, logger slog.Logger, handler http.Handler, addr, name string) (closeFunc func()) {
 	logger.Debug(ctx, "http server listening", slog.F("addr", addr), slog.F("name", name))
 
-	srv := &http.Server{Addr: addr, Handler: handler}
+	srv := &http.Server{
+		Addr:              addr,
+		Handler:           handler,
+		ReadHeaderTimeout: time.Minute,
+	}
 	go func() {
 		err := srv.ListenAndServe()
 		if err != nil && !xerrors.Is(err, http.ErrServerClosed) {