Demo: Zero-to-Micropay

GoLang

Pre-requisites

Steps

In this tutorial you will build a demo app that will:

In order to interact with Hedera you need a Hedera Account ID, the DNS or IP Address plus the Port Number for a Hedera node, and the Node ID of that node. All of those things can be acquired through the Hedera portal.

Your Account ID and the Node ID are both Account IDs. Account IDs are made up of three integers representing the shard ID, the realm ID, and your account number in that shard and realm. It looks like this: 0:0:1001, which represents account number 1001 in realm 0 in shard 0.

  1. Create a file called main.go
  2. Open main.go in the IDE/editor of your choice

  3. Connect to Hedera

     package main

 import (
     "fmt"
     "time"

     "github.com/hashgraph/hedera-sdk-go"
 )

 func main() {

    Establish connection to the Hedera node by using the testnet Address and Port shown in the Hedera portal. Be sure to replace the example 50123 to your specific port.

    Defer the disconnection of the connection to guarantee a clean disconnect from the node.

     client := hedera.Dial("testnet.hedera.com:50123")
 if err != nil {
     panic(err)
 }
 defer client.Close()

    Initialise the myAccount variable based on your Account ID from the portal. Ensure that you replace the example 1099 with your own Account ID.

     myAccount := hedera.NewAccountID(0, 0, 1099)

  4. Get your account balance

    GetAccountBalance constructs the request; adding .Answer() executes the request. Don’t forget error-handling.

    fmt.Printf can then output the balance.

     myBalance, err := client.GetAccountBalance(myAccount).Answer()
 if err != nil {
     panic(err)
 }

 fmt.Printf("Your balance: %v \n", myBalance)

    Finally, close the braces for func main.

     }

    Note: Before performing any other operations, be aware that testnets are throttled and may respond with an error if requests are made to the Hedera API to frequently. For this reason it is best practice to add a sleep timer inbetween requests.

     time.Sleep(1 * time.Second)

  5. Transfer hbars to another account

    The secret key associated with your Hedera account is required to sign all transactions submitted to Hedera. You can learn about how to generate those keys in the creating keys document.

    The term “operator” used in the naming of the next variable operatorSecret is used to highlight the fact that this is the account responsible for submitting the transaction. Ensure that your replace <my-secret-key> with your own secret key in the following code block:

     operatorSecret, err := hedera.SecretKeyFromString("<my-secret-key>")
 if err != nil {
     panic(err)
 }

    The next statement is more complex as it takes advantage of the builder pattern. The statement is included in its entirety; each line is explained individually below. Take care to replace 1099 with your account number and 1100 with the account number of the recipient of your transfer.

     response, err := client.CryptoTransfer().
     Operator(hedera.NewAccountID(0, 0, 1099)).
     Node(hedera.NewAccountID(0, 0, 3)).
     Transfer(hedera.NewAccountID(0, 0, 1099), -1).
     Transfer(hedera.NewAccountID(0, 0, 1100), 1).
     Sign(operatorSecret).
     Sign(operatorSecret).
     Execute()
 if err != nil {
     panic(err)
 }

    • Line 1: response, err := client.CryptoTransfer(). creates a transaction to transfer hbars between accounts.

    • Line 2: Operator(hedera.NewAccountID(0, 0, 1099)). identifies the account initiating the transaction.

    • Line 3: Node(hedera.NewAccountID(0, 0, 3)). identifies the account of the Hedea node to which the transaction is being sent.

    • Line 4: Transfer(hedera.NewAccountID(0, 0, 1099), -1). sets up a transfer, which pairs an account with a signed integer. In this case, the account is your account and the amount is -1. The negative number indicates that the balance of your account will be decremented by this amount.

    • Line 5: Transfer(hedera.NewAccountID(0, 0, 1100), 1). creates a second transfer, pairing an account with a signed integer. In this case, the account is your friend’s account and the amount is 1. The positive number indicates that the balance of your account will be incremented by this amount. Important: the sum of all transfers contained within in a CryptoTransfer must equal zero.

    • Lines 6 and 7: Sign(operatorSecret). adds a signature based on a secret key. It is necessary to repeat this line to sign as both operator initiating the transfer transaction and account holder associated with an outgoing (negative) transfer – even though both keys are the same.

    • Line 8: Execute() executes the transaction.

    Next, the ID of the transaction itself is captured from the response in the above statement. The transactionID is made up of the account ID and the transaction timestamp right down to nanoseconds.

     transactionID := response.ID

 time.Sleep(1 * time.Second)

    You can now request a receipt and print the status using the following code. Although this is not a mandatory step, it does verify that your transaction successfully reached network consensus.

     receipt, err := client.GetTransactionReceipt(transactionID).Answer()
 if err != nil {
     panic(err)
 }

 fmt.Printf("Transfer Transaction Status: %v \n", receipt.Status)

 time.Sleep(1 * time.Second)

    A status code of 1 indicates success.

    Finally, you can requery the balance of both accounts to verify that 1 hbar was indeed transferred from your account to that of your friend.

     myBalance, err = client.GetAccountBalance(myAccount).Answer()
 if err != nil {
     panic(err)
 }

 fmt.Printf("Your new balance: %v \n", myBalance)

 time.Sleep(1 * time.Second)

 otherAccount := hedera.NewAccountID(0, 0, 1100)

 otherBalance, err = client.GetAccountBalance(otherAccount).Answer()
 if err != nil {
     panic(err)
 }

 fmt.Printf("Friend new balance: %v \n", otherBalance)
  6. Run the program again by executing: 
     $> go run main.go

You have just completed our demo application for facilitating micropayment transactions. Congratulations!