s5cmd cp hangs on named pipes/socketfiles

[bforcier1]

When uploading to S3, if s5cmd encounters a socketfile or named pipe, it will hang. It should either skip these by default, or have an option to skip them:

awscli: aws s3 cp pipe.fifo s3://chainlink000-bforcier-scratch-01/warning: Skipping file pipe.fifo. File is character special device, block special device, FIFO, or socket.

s5cmd (hangs forever): s5cmd cp pipe.fifo s3://my-bucket/