Error in the Router.ex

I am following the tutorial reactnative with phoenix , after setting up my initial setup , I wrote the following code in the Router.ex

scope "/api", do
    pipe_through :api

    forward "/graphql", Absinthe.Plug,
    schema: CroonkWeb.Schema

    if Mix.env == :dev do
    forward "/graphiql", Absinthe.Plug.Graphiql,
    schema: CroonkWeb.Schema

while compiling it throws the error,

Compilation error in file lib/croonk_web/router.ex ==
** (SyntaxError) lib/croonk_web/router.ex:8: unexpected token: do. In case you wanted to write a "do" expression, you must either use do-blocks or separate the keyword argument with comma. For example, you should either write:

    if some_condition? do

or the equivalent construct:

    if(some_condition?, do: :this, else: :that)

where "some_condition?" is the first argument and the second argument is a keyword list
    (elixir) lib/kernel/parallel_compiler.ex:208: anonymous fn/4 in Kernel.ParallelCompiler.spawn_workers/6

I followed everything as per the tutorial ,it works better in the tutorial . In tutorial they are using phoenix 1.3 Iam using Phoenix 1.4… Please help me overcome this. thanks.

Remove the comma in the first line.