code: func (c *ACMPCA) GetCertificateAuthorityCsr(input *GetCertificateAuthorityCsrInput) (*GetCertificateAuthorityCsrOutput, error) {
  	req, out := c.GetCertificateAuthorityCsrRequest(input)
  	return out, req.Send()
  }
docs: // GetCertificateAuthorityCsr API operation for AWS Certificate Manager Private Certificate Authority.
  //
  // Retrieves the certificate signing request (CSR) for your private certificate
  // authority (CA). The CSR is created when you call the CreateCertificateAuthority
  // operation. Take the CSR to your on-premises X.509 infrastructure and sign
  // it by using your root or a subordinate CA. Then import the signed certificate
  // back into ACM PCA by calling the ImportCertificateAuthorityCertificate operation.
  // The CSR is returned as a base64 PEM-encoded string.
  //
  // Returns awserr.Error for service API and SDK errors. Use runtime type assertions
  // with awserr.Error's Code and Message methods to get detailed information about
  // the error.
  //
  // See the AWS API reference guide for AWS Certificate Manager Private Certificate Authority's
  // API operation GetCertificateAuthorityCsr for usage and error information.
  //
  // Returned Error Codes:
  //   * ErrCodeRequestInProgressException "RequestInProgressException"
  //   Your request is already in progress.
  //
  //   * ErrCodeRequestFailedException "RequestFailedException"
  //   The request has failed for an unspecified reason.
  //
  //   * ErrCodeResourceNotFoundException "ResourceNotFoundException"
  //   A resource such as a private CA, S3 bucket, certificate, or audit report
  //   cannot be found.
  //
  //   * ErrCodeInvalidArnException "InvalidArnException"
  //   The requested Amazon Resource Name (ARN) does not refer to an existing resource.
  //
  //   * ErrCodeInvalidStateException "InvalidStateException"
  //   The private CA is in a state during which a report or certificate cannot
  //   be generated.
  //
  // See also, https://docs.aws.amazon.com/goto/WebAPI/acm-pca-2017-08-22/GetCertificateAuthorityCsr