use locally checked out lib in the docker job

see https://github.com/mattn/go-sqlite3/pull/1177

.github/workflows/docker.yaml

@@ -17,6 +17,5 @@ jobs:
 
       - name: Run example - simple
         run: |
-          cd ./_example/simple
-          docker build -t simple .
+          docker build -t simple -f ./_example/simple/Dockerfile .
           docker run simple | grep 99\ こんにちは世界099

_example/simple/Dockerfile

@@ -26,7 +26,9 @@ WORKDIR /workspace
 COPY . /workspace/
 
 RUN \
+    cd _example/simple && \
     go mod init github.com/mattn/sample && \
+    go mod edit -replace=github.com/mattn/go-sqlite3=../.. && \
     go mod tidy && \
     go install -ldflags='-s -w -extldflags "-static"' ./simple.go