Fix inconsistency regarding default port env var (elixir-lang#1367)

Hoffs · web-flow · commit be1471be68ea · 2020-02-16T13:31:13.000+01:00
Very similar to elixir-lang#1172 which missed last rewrite part that still raised error if env variable was not present.
diff --git a/getting-started/mix-otp/task-and-gen-tcp.markdown b/getting-started/mix-otp/task-and-gen-tcp.markdown
@@ -297,7 +297,7 @@ We could fix this by defining our own module that calls `use Task, restart: :per
 
 ```elixir
 def start(_type, _args) do
- port = String.to_integer(System.get_env("PORT") || raise "missing $PORT environment variable")
+ port = String.to_integer(System.get_env("PORT") || "4040")
 
 children = [
{Task.Supervisor, name: KVServer.TaskSupervisor},

-Original file line number
+Diff line change
 ```elixir
 defstart(_type, _args) do
 - port =String.to_integer(System.get_env("PORT") ||raise"missing $PORT environment variable")
 + port =String.to_integer(System.get_env("PORT") ||"4040")
  children = [
 {Task.Supervisor, name:KVServer.TaskSupervisor},