fix go-target.md, remove duplicate get

Signed-off-by: 朱少飞 <42376488+css521@users.noreply.github.com>
diff --git a/doc/go-target.md b/doc/go-target.md
index 6cc52a5..22864b4 100644
--- a/doc/go-target.md
+++ b/doc/go-target.md
@@ -78,7 +78,7 @@
 using the standard.
 
 ```shell
-go get -u get github.com/antlr4-go/antlr
+go get -u github.com/antlr4-go/antlr
 ```
 
 If you have not yet upgraded existing projects to the `/v4` module path, consult the section *Upgrading to v4