I need to save the request body to a file. Something like this:

post {
   val targetChannel = FileOutputStream(Files.createTempFile("job-", ".json").toFile()).channel
   val originChannel = newChannel(call.receiveStream())

   originChannel.use {
       targetChannel.use {
            targetChannel.transferFrom(originChannel, 0L, 100000)
       }
    }
...

FileOutputStream, etc. are blocking calls. Is there a nonblocking API to write to files so I can use

receiveChannel()

?

You can use a

ByteWriteChannel

instance created from a file to copy bytes from input to output channel:

post {
    val tmpFile = Files.createTempFile("job-", ".json").toFile()
    call.receiveChannel().copyTo(tmpFile.writeChannel())
}

Very nice!

Better use

call.receiveChannel().copyAndClose(tmpFile.writeChannel())

instead