doctl 1.21.0

Closes #41906.

Signed-off-by: FX Coudert <fxcoudert@gmail.com>

Formula/doctl.rb

@@ -1,8 +1,8 @@
 class Doctl < Formula
   desc "Command-line tool for DigitalOcean"
   homepage "https://github.com/digitalocean/doctl"
-  url "https://github.com/digitalocean/doctl/archive/v1.20.1.tar.gz"
-  sha256 "bfd0209ab6a10ace41d17608f546a19e806c92f818be2ed0d4bfe8ab256c8a69"
+  url "https://github.com/digitalocean/doctl/archive/v1.21.0.tar.gz"
+  sha256 "5f449c0b66998c5d0a42e70901c2feb13b6bffea844ce2ea3e137325c26df283"
   head "https://github.com/digitalocean/doctl.git"
 
   bottle do
@@ -15,21 +15,23 @@ class Doctl < Formula
   depends_on "go" => :build
 
   def install
+    ENV["GO111MODULE"] = "on"
     ENV["GOPATH"] = buildpath
 
-    mkdir_p buildpath/"src/github.com/digitalocean/"
-    ln_sf buildpath, buildpath/"src/github.com/digitalocean/doctl"
-
     doctl_version = version.to_s.split(/\./)
-    base_flag = "-X github.com/digitalocean/doctl"
-    ldflags = %W[
-      #{base_flag}.Major=#{doctl_version[0]}
-      #{base_flag}.Minor=#{doctl_version[1]}
-      #{base_flag}.Patch=#{doctl_version[2]}
-      #{base_flag}.Label=release
-    ].join(" ")
-    system "go", "build", "-ldflags", ldflags, "github.com/digitalocean/doctl/cmd/doctl"
-    bin.install "doctl"
+
+    src = buildpath/"src/github.com/digitalocean/doctl"
+    src.install buildpath.children
+    src.cd do
+      base_flag = "-X github.com/digitalocean/doctl"
+      ldflags = %W[
+        #{base_flag}.Major=#{doctl_version[0]}
+        #{base_flag}.Minor=#{doctl_version[1]}
+        #{base_flag}.Patch=#{doctl_version[2]}
+        #{base_flag}.Label=release
+      ].join(" ")
+      system "go", "build", "-ldflags", ldflags, "-o", bin/"doctl", "github.com/digitalocean/doctl/cmd/doctl"
+    end
 
     (bash_completion/"doctl").write `#{bin}/doctl completion bash`
     (zsh_completion/"doctl").write `#{bin}/doctl completion zsh`