.github/workflows, build: install dlv in containers

Tests now require dlv

Change-Id: I3e144cb08938c98f661b480772bd62bdc971ea24
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/251084
Reviewed-by: Robert Findley <rfindley@google.com>

.github/workflows/release-nightly.yml

@@ -58,6 +58,7 @@ jobs:
             go get github.com/cweill/gotests/...
             go get github.com/rogpeppe/godef
             go get github.com/ramya-rao-a/go-outline
+            go get github.com/go-delve/delve/cmd/dlv
         env:
           GO111MODULE: on   
 

.github/workflows/test-long.yml

@@ -57,6 +57,7 @@ jobs:
             go get github.com/cweill/gotests/...
             go get github.com/rogpeppe/godef
             go get github.com/ramya-rao-a/go-outline
+            go get github.com/go-delve/delve/cmd/dlv
         env:
           GO111MODULE: on   
           

.github/workflows/test-smoke.yml

@@ -53,6 +53,7 @@ jobs:
             go get github.com/cweill/gotests/...
             go get github.com/rogpeppe/godef
             go get github.com/ramya-rao-a/go-outline
+            go get github.com/go-delve/delve/cmd/dlv
         env:
           GO111MODULE: on             
       

build/Dockerfile

@@ -32,7 +32,8 @@ RUN GO111MODULE=on go get -x -v github.com/acroca/go-symbols && \
 	GO111MODULE=on go get -x -v github.com/uudashr/gopkgs/v2/cmd/gopkgs && \
 	GO111MODULE=on go get -x -v github.com/zmb3/gogetdoc && \
 	GO111MODULE=on go get -x -v golang.org/x/lint/golint && \
-	GO111MODULE=on go get -x -v golang.org/x/tools/cmd/gorename
+	GO111MODULE=on go get -x -v golang.org/x/tools/cmd/gorename && \
+	GO111MODULE=on go get -x -v github.com/go-delve/delve/cmd/dlv
 
 WORKDIR /workspace
 ENTRYPOINT ["build/all.bash"]