code: func (c *Redshift) PurchaseReservedNodeOffering(input *PurchaseReservedNodeOfferingInput) (*PurchaseReservedNodeOfferingOutput, error) {
  	req, out := c.PurchaseReservedNodeOfferingRequest(input)
  	return out, req.Send()
  }
docs: // PurchaseReservedNodeOffering API operation for Amazon Redshift.
  //
  // Allows you to purchase reserved nodes. Amazon Redshift offers a predefined
  // set of reserved node offerings. You can purchase one or more of the offerings.
  // You can call the DescribeReservedNodeOfferings API to obtain the available
  // reserved node offerings. You can call this API by providing a specific reserved
  // node offering and the number of nodes you want to reserve.
  //
  // For more information about reserved node offerings, go to Purchasing Reserved
  // Nodes (https://docs.aws.amazon.com/redshift/latest/mgmt/purchase-reserved-node-instance.html)
  // in the Amazon Redshift Cluster Management Guide.
  //
  // 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 Amazon Redshift's
  // API operation PurchaseReservedNodeOffering for usage and error information.
  //
  // Returned Error Codes:
  //   * ErrCodeReservedNodeOfferingNotFoundFault "ReservedNodeOfferingNotFound"
  //   Specified offering does not exist.
  //
  //   * ErrCodeReservedNodeAlreadyExistsFault "ReservedNodeAlreadyExists"
  //   User already has a reservation with the given identifier.
  //
  //   * ErrCodeReservedNodeQuotaExceededFault "ReservedNodeQuotaExceeded"
  //   Request would exceed the user's compute node quota. For information about
  //   increasing your quota, go to Limits in Amazon Redshift (https://docs.aws.amazon.com/redshift/latest/mgmt/amazon-redshift-limits.html)
  //   in the Amazon Redshift Cluster Management Guide.
  //
  //   * ErrCodeUnsupportedOperationFault "UnsupportedOperation"
  //   The requested operation isn't supported.
  //
  // See also, https://docs.aws.amazon.com/goto/WebAPI/redshift-2012-12-01/PurchaseReservedNodeOffering