Resolved: Unexpected Result When Using Fibers

#! /usr/bin/env ruby
#encoding: utf-8
#frozen_string_literal: true

sg = Fiber.new do
  File.open(begin print "Enter filename: "; gets.chomp end).each{|l| Fiber.yield l}
end

begin
  loop do
    puts sg.resume
  end
rescue => err
  puts "Error: #{err.message}"
end

This is the first
This is the second
This is the third
This is the fourth
This is the fifth

Enter filename: datafile
This is the first
This is the second
This is the third
This is the fourth
This is the fifth
#<File:0x0000557ce26ce3c8>
Error: attempt to resume a terminated fiber

File.open(begin print "Enter filename: "; gets.chomp end).each{|l| Fiber.yield l}

"This is the first"
"This is the second"
"This is the third"
"This is the fourth"
"This is the fifth"
(the file object itself)

sg = Fiber.new do
  print "Enter filename: "
  filename = gets.chomp
  # By passing File.open a block, the file is closed after the block automatically.
  File.open(filename) do |f|
    f.each{|l| Fiber.yield l}
  end
  # Our fiber has to return something at the end, so let's just return nil
  nil
end

begin
  loop do
    # Get the value. If it's nil, then we're done; we can break out of the loop.
    # Otherwise, print it
    value = sg.resume
    break if value.nil?
    puts value
  end
rescue => err
  puts "Error: #{err.message}"
end