unable to verify the first certificate

[seraphjiang]

$ node dynamoDBtoCSV.js -t swift-us-east-1-prod.table1 -ec

{ Error: unable to verify the first certificate
    at TLSSocket.onConnectSecure (_tls_wrap.js:1051:34)
    at TLSSocket.emit (events.js:189:13)
    at TLSSocket.EventEmitter.emit (domain.js:441:20)
    at TLSSocket._finishInit (_tls_wrap.js:633:8)
  message: 'unable to verify the first certificate',
  code: 'NetworkingError',
  region: 'us-east-1',
  hostname: 'c',
  retryable: true,
  time: 2019-10-28T21:49:37.197Z }