Your first lamport — a real devnet transaction

// main.go — send 0.01 SOL and inspect the result
// dep: github.com/gagliardetto/solana-go  (go get github.com/gagliardetto/solana-go)
package main

import (
	"context"
	"fmt"
	"os"

	"github.com/gagliardetto/solana-go"
	"github.com/gagliardetto/solana-go/programs/system"
	"github.com/gagliardetto/solana-go/rpc"
	confirm "github.com/gagliardetto/solana-go/rpc/sendAndConfirmTransaction"
	"github.com/gagliardetto/solana-go/rpc/ws"
)

const LAMPORTS_PER_SOL = 1_000_000_000

func main() {
	ctx := context.Background()

	// Connect to devnet
	client := rpc.New(rpc.DevNet_RPC)
	wsClient, err := ws.Connect(ctx, rpc.DevNet_WS)
	if err != nil {
		panic(err)
	}

	// Load your local keypair (~/.config/solana/id.json)
	from, err := solana.PrivateKeyFromSolanaKeygenFile(
		os.Getenv("HOME") + "/.config/solana/id.json",
	)
	if err != nil {
		panic(err)
	}

	// A random friend (replace with theirs)
	to := solana.MustPublicKeyFromBase58("SomeFriendPubkeyHere1111111111111111111111")

	// Build the transfer instruction
	recent, err := client.GetLatestBlockhash(ctx, rpc.CommitmentConfirmed)
	if err != nil {
		panic(err)
	}

	tx, err := solana.NewTransaction(
		[]solana.Instruction{
			system.NewTransferInstruction(
				uint64(0.01*LAMPORTS_PER_SOL),
				from.PublicKey(),
				to,
			).Build(),
		},
		recent.Value.Blockhash,
		solana.TransactionPayer(from.PublicKey()),
	)
	if err != nil {
		panic(err)
	}

	_, err = tx.Sign(func(key solana.PublicKey) *solana.PrivateKey {
		if key.Equals(from.PublicKey()) {
			return &from
		}
		return nil
	})
	if err != nil {
		panic(err)
	}

	sig, err := confirm.SendAndConfirmTransaction(ctx, client, wsClient, tx)
	if err != nil {
		panic(err)
	}

	fmt.Println("Tx:", sig)
	fmt.Println("Explorer: https://solscan.io/tx/" + sig.String() + "?cluster=devnet")

	// Fetch and inspect the confirmed transaction
	version := uint64(0)
	full, err := client.GetTransaction(ctx, sig, &rpc.GetTransactionOpts{
		MaxSupportedTransactionVersion: &version,
		Commitment:                     rpc.CommitmentConfirmed,
	})
	if err != nil {
		panic(err)
	}

	fmt.Println("Fee paid:", full.Meta.Fee, "lamports")
	fmt.Println("Pre-balances:", full.Meta.PreBalances)
	fmt.Println("Post-balances:", full.Meta.PostBalances)
}