Upgrade golang to v1.16

Dockerfile

@@ -138,8 +138,8 @@ RUN add-apt-repository ppa:ondrej/php \
 ### GO
 
 # Install Go and dep
-ARG GOLANG_VERSION=1.15.7
-ARG GOLANG_CHECKSUM=0d142143794721bb63ce6c8a6180c4062bcf8ef4715e7d6d6609f3a8282629b3
+ARG GOLANG_VERSION=1.16.2
+ARG GOLANG_CHECKSUM=542e936b19542e62679766194364f45141fde55169db2d8d01046555ca9eb4b8
 RUN curl --http1.1 -o go.tar.gz https://dl.google.com/go/go${GOLANG_VERSION}.linux-amd64.tar.gz \
   && echo "$GOLANG_CHECKSUM go.tar.gz" | sha256sum -c - \
   && tar -xzf go.tar.gz -C /opt \

go_modules/lib/dependabot/go_modules/resolvability_errors.rb

@@ -15,16 +15,17 @@ def self.handle(message, credentials:)
           SharedHelpers.with_git_configured(credentials: credentials) do
             File.write("go.mod", "module dummy\n")
 
-            env = { "GOPRIVATE" => "*" }
-            _, _, status = Open3.capture3(env, SharedHelpers.escape_command("go get #{mod_path}"))
-            raise Dependabot::DependencyFileNotResolvable, message if status.success?
-
             mod_split = mod_path.split("/")
             repo_path = if mod_split.size > 3
                           mod_split[0..2].join("/")
                         else
                           mod_path
                         end
+
+            env = { "GOPRIVATE" => "*" }
+            _, _, status = Open3.capture3(env, SharedHelpers.escape_command("go list -m -versions #{repo_path}"))
+            raise Dependabot::DependencyFileNotResolvable, message if status.success?
+
             raise Dependabot::GitDependenciesNotReachable, [repo_path]
           end
         end

go_modules/spec/dependabot/go_modules/file_updater/go_mod_updater_spec.rb

@@ -103,6 +103,13 @@
           it { is_expected.to include("go 1.13") }
         end
 
+        context "when a retract directive is present" do
+          let(:project_name) { "go_retracted" }
+
+          it { is_expected.to include("// reason for retraction") }
+          it { is_expected.to include("retract v1.0.5") }
+        end
+
         describe "a dependency who's module path has changed (inc version)" do
           let(:project_name) { "module_path_and_version_changed" }
 
@@ -229,16 +236,12 @@
             # OpenAPIV2 has been renamed to openapiv2 in this version
             let(:dependency_version) { "v0.5.1" }
 
-            # NOTE: We explitly don't want to raise a resolvability error from go mod tidy
-            it "does not raises a DependencyFileNotResolvable error" do
+            it "raises a DependencyFileNotResolvable error" do
+              error_class = Dependabot::DependencyFileNotResolvable
               expect { updater.updated_go_sum_content }.
-                to_not raise_error
-            end
-
-            it "updates the go.mod" do
-              expect(updater.updated_go_mod_content).to include(
-                %(github.com/googleapis/gnostic v0.5.1 // indirect\n)
-              )
+                to raise_error(error_class) do |error|
+                expect(error.message).to include("googleapis/gnostic/OpenAPIv2")
+              end
             end
           end
         end

go_modules/spec/fixtures/projects/go_retracted/go.mod

@@ -0,0 +1,10 @@
+module github.com/dependabot/vgotest
+
+go 1.16
+
+require (
+	rsc.io/quote v1.4.0
+)
+
+// reason for retraction
+retract v1.0.5

go_modules/spec/fixtures/projects/go_retracted/main.go

@@ -0,0 +1,8 @@
+package main
+
+import (
+	_ "rsc.io/quote"
+)
+
+func main() {
+}