Revert "Remove `-race` from CI build."

This reverts commit 486b578f6a.

.gitlab-ci.yml

@@ -39,7 +39,7 @@ compile:
   script:
     - echo "${CI_JOB_ID}" > CI_JOB_ID.txt
       -buildmode=pie -ldflags -extldflags=-Wl,-z,now,-z,relro
-    - env GOOS=linux GOARCH=amd64 go build -buildmode=pie -ldflags "-extldflags=-Wl,-z,now,-z,relro '-static'" -o $CI_PROJECT_DIR/linux-amd64/go-sendxmpp
+    - env GOOS=linux GOARCH=amd64 go build -buildmode=pie -race -ldflags "-extldflags=-Wl,-z,now,-z,relro '-static'" -o $CI_PROJECT_DIR/linux-amd64/go-sendxmpp
     - env GOOS=linux GOARCH=arm64 go build -buildmode=pie -ldflags "-extldflags=-Wl,-z,now,-z,relro '-static'" -o $CI_PROJECT_DIR/linux-arm64/go-sendxmpp
     - env GOOS=linux GOARCH=386 go build -buildmode=pie -ldflags "-extldflags=-Wl,-z,now,-z,relro '-static'" -o $CI_PROJECT_DIR/linux-386/go-sendxmpp
     - env GOOS=linux GOARCH=arm go build -buildmode=pie -ldflags "-extldflags=-Wl,-z,now,-z,relro '-static'" -o $CI_PROJECT_DIR/linux-arm/go-sendxmpp