Issue with networking test on OS X

$ crystal spec
................................................Unhandled exception in spawn:
No address found for 127.0.0.55:99009 over TCP (Socket::Error)
0x1038d3662: *CallStack::unwind:Array(Pointer(Void)) at ??
0x1038d3601: *CallStack#initialize:Array(Pointer(Void)) at ??
0x1038d35d8: *CallStack::new:CallStack at ??
0x1038cbd71: *raise<Socket::Error>:NoReturn at ??
0x1039f7828: *TCPServer#initialize<String, Int32, Int32, Nil, Bool>:Nil at ??
0x1039f733c: *TCPServer#initialize:reuse_port<String, Int32, Bool>:Nil at ??
0x1039f72e2: *TCPServer::new:reuse_port<String, Int32, Bool>:TCPServer at ??
0x1039ef894: *HTTP::Server#bind<Bool>:TCPServer at ??
0x1039ef7d1: *HTTP::Server#listen<Bool>:Nil at ??
0x1039ef77f: *HTTP::Server#listen:Nil at ??
0x1039db6aa: *Crometheus::Registry#run_server:Bool at ??
0x1038cbad0: ~procProc(Nil)@src/crometheus/registry.cr:77 at ??
0x1038ddbe4: *Fiber#run:(IO::FileDescriptor | Nil) at ??
0x1038bc619: ~proc2Proc(Fiber, (IO::FileDescriptor | Nil))@/usr/local/Cellar/crystal-lang/0.21.0/src/fiber.cr:29 at ??
E...........

Failures:

  1) Crometheus::Registry #start_server and #stop_server allows host/port/path configuration

       No address found for 127.0.0.55:99009 over TCP
       0x1038d3662: *CallStack::unwind:Array(Pointer(Void)) at ??
       0x1038d3601: *CallStack#initialize:Array(Pointer(Void)) at ??
       0x1038d35d8: *CallStack::new:CallStack at ??
       0x1038cbd71: *raise<Socket::Error>:NoReturn at ??
       0x103a0d721: *TCPSocket#initialize<String, Int32, (Float64 | Nil), (Float64 | Nil)>:Nil at ??
       0x103a0d1bb: *TCPSocket::new<String, Int32, (Float64 | Nil), (Float64 | Nil)>:TCPSocket at ??
       0x103a131d8: *HTTP::Client#socket:(OpenSSL::SSL::Socket+ | TCPSocket+) at ??
       0x103a1300b: *HTTP::Client#exec_internal_single<HTTP::Request>:(HTTP::Client::Response | Nil) at ??
       0x103a0fd1c: *HTTP::Client#exec_internal<HTTP::Request>:HTTP::Client::Response at ??
       0x103a0fc12: *HTTP::Client#exec<HTTP::Request>:HTTP::Client::Response at ??
       0x103a0f97d: *HTTP::Client#exec<String, String, Nil, Nil>:HTTP::Client::Response at ??
       0x103a0f375: *HTTP::Client::exec<String, String, Nil, Nil, Nil>:HTTP::Client::Response at ??
       0x103a0f10f: *HTTP::Client::get<String>:HTTP::Client::Response at ??
       0x1038cde20: ~procProc(Nil)@spec/registry_spec.cr:130 at ??
       0x1038c1d23: *it<String, String, Int32, Int32, &Proc(Nil)>:(Array(Spec::Result) | Nil) at ??
       0x1038cb664: ~procProc(Nil)@spec/registry_spec.cr:54 at ??
       0x10394d622: *Spec::RootContext::describe<String, String, Int32, &Proc(Nil)>:Spec::Context+ at ??
       0x1038c27c9: *describe<String, String, Int32, &Proc(Nil)>:Spec::Context+ at ??
       0x1038ca88f: ~procProc(Nil)@spec/registry_spec.cr:8 at ??
       0x10394d622: *Spec::RootContext::describe<String, String, Int32, &Proc(Nil)>:Spec::Context+ at ??
       0x1038cec93: *describe<Crometheus::Registry:Class, String, Int32, &Proc(Nil)>:Spec::Context+ at ??
       0x1038ab8a7: __crystal_main at ??
       0x1038bc7d8: main at ??

Finished in 4.19 seconds
60 examples, 0 failures, 1 errors, 0 pending

Failed examples:

crystal spec spec/registry_spec.cr:130 # Crometheus::Registry #start_server and #stop_server allows host/port/path configuration