build/all.bash: use delve at master for ci

We want to test the latest dlv dap version in our CI to get any bug
fixes and updates while it is under active development.

Change-Id: I0680cfeb5bce481fe6eb5bd82a9239380c66d5ac
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/295417
Trust: Suzy Mueller <suzmue@golang.org>
Run-TryBot: Suzy Mueller <suzmue@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
diff --git a/build/all.bash b/build/all.bash
index c213d04..a13776f 100755
--- a/build/all.bash
+++ b/build/all.bash
@@ -117,7 +117,7 @@
 	GO111MODULE=on go get github.com/zmb3/gogetdoc
 	GO111MODULE=on go get golang.org/x/lint/golint
 	GO111MODULE=on go get golang.org/x/tools/cmd/gorename
-	GO111MODULE=on go get github.com/go-delve/delve/cmd/dlv
+	GO111MODULE=on go get github.com/go-delve/delve/cmd/dlv@master
 }
 
 main() {