.github/workflows: update actions/setup-go to v2

v2 adds GOBIN (or GOPATH/bin) to the PATH
which is necessary to locate installed tools
because we no longer activates the extension through
activate that triggered mutation of GOPATH/GOBIN
environment variables.

Change-Id: I3e590b63e1f6d0dd6c4bf845b4cd4087c609184d
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/268997
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Suzy Mueller <suzmue@golang.org>
diff --git a/.github/workflows/release-nightly.yml b/.github/workflows/release-nightly.yml
index bb2fc21..f232d3f 100644
--- a/.github/workflows/release-nightly.yml
+++ b/.github/workflows/release-nightly.yml
@@ -27,7 +27,7 @@
           node-version: '10.x'
 
       - name: Setup Go
-        uses: actions/setup-go@v1
+        uses: actions/setup-go@v2
         with:
          go-version: '1.15'
 
diff --git a/.github/workflows/test-long.yml b/.github/workflows/test-long.yml
index ca0bcd5..4b129a0 100644
--- a/.github/workflows/test-long.yml
+++ b/.github/workflows/test-long.yml
@@ -31,7 +31,7 @@
           node-version: '10.x'
 
       - name: Setup Go
-        uses: actions/setup-go@v1
+        uses: actions/setup-go@v2
         with:
          go-version: '1.15'
 
diff --git a/.github/workflows/test-smoke.yml b/.github/workflows/test-smoke.yml
index fb12a33..941cfc3 100644
--- a/.github/workflows/test-smoke.yml
+++ b/.github/workflows/test-smoke.yml
@@ -27,7 +27,7 @@
           node-version: '10.x'
 
       - name: Setup Go
-        uses: actions/setup-go@v1
+        uses: actions/setup-go@v2
         with:
          go-version: '1.15'