code: func calcMinRequiredTxRelayFee(serializedSize int64, minRelayTxFee btcutil.Amount) int64 {
  	// Calculate the minimum fee for a transaction to be allowed into the
  	// mempool and relayed by scaling the base fee (which is the minimum
  	// free transaction relay fee).  minTxRelayFee is in Satoshi/kB so
  	// multiply by serializedSize (which is in bytes) and divide by 1000 to
  	// get minimum Satoshis.
  	minFee := (serializedSize * int64(minRelayTxFee)) / 1000
  
  	if minFee == 0 && minRelayTxFee > 0 {
  		minFee = int64(minRelayTxFee)
  	}
  
  	// Set the minimum fee to the maximum possible value if the calculated
  	// fee is not in the valid range for monetary amounts.
  	if minFee < 0 || minFee > btcutil.MaxSatoshi {
  		minFee = btcutil.MaxSatoshi
  	}
  
  	return minFee
  }
docs: // calcMinRequiredTxRelayFee returns the minimum transaction fee required for a
  // transaction with the passed serialized size to be accepted into the memory
  // pool and relayed.