iGoat-Swift igoat_server.rb not working.

[vedant3005]

Error:

$ ./igoat_server.rb
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/universal-darwin19/rbconfig.rb:229: warning: Insecure world writable dir /usr/local/opt in PATH, mode 04077
Traceback (most recent call last):
2: from ./igoat_server.rb:57:in <main>' 1: from /Library/Ruby/Site/2.6.0/rubygems/core_ext/kernel_require.rb:92:in require'
/Library/Ruby/Site/2.6.0/rubygems/core_ext/kernel_require.rb:92:in `require': cannot load such file -- sinatra/base (LoadError)

System Config:
Mac os: Cataline 10.15.6
Ruby Version: ruby 2.6.3p62 (2019-04-16 revision 67580) [universal.x86_64-darwin19]