diff --git a/go.mod b/go.mod
index eb2f6d4..a3d78b4 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/shogo82148/actions-goveralls
 
-go 1.21.6
+go 1.20
 
 require github.com/mattn/goveralls v0.0.12
 
diff --git a/run-in-docker.sh b/run-in-docker.sh
index 9e9773c..7c2ad5b 100755
--- a/run-in-docker.sh
+++ b/run-in-docker.sh
@@ -8,4 +8,4 @@ docker run --rm \
     -v actions-goveralls-cache:/go/pkg/mod \
     -v actions-goveralls-cache:/root/.cache \
     -v "$CURRENT":/go/src/github.com/shogo82148/actions-goveralls \
-    -w /go/src/github.com/shogo82148/actions-goveralls golang:1.21.6 "$@"
+    -w /go/src/github.com/shogo82148/actions-goveralls golang:1.21.0 "$@"