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The CCTP Go SDK provides default RPC endpoints for all supported chains, but you can easily override them with your own custom endpoints from providers like Alchemy, Infura, or your own infrastructure.

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What This Example Demonstrates

  • How to get chains with default RPC endpoints
  • Using chain name constants for type safety
  • Applying custom RPC overrides
  • IDE autocomplete support for chain names

​
Complete Code Example

This example shows how to use the ApplyRPCOverrides function: 
package main

import (
    "github.com/circlefin/cctp-go"
)

func main() {
    // Get chains with default RPC endpoints
    chains := cctp.GetChains(false) // false = mainnet

    // Define custom RPC endpoints using the chain name constants
    // This provides IDE autocomplete and prevents typos
    customRPCs := map[string]string{
        cctp.Ethereum: "https://eth-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
        cctp.Arbitrum: "https://arb-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
        cctp.Base:     "https://base-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
    }

    // Apply RPC overrides
    chains = cctp.ApplyRPCOverrides(chains, customRPCs)

    // Now use chains with your custom RPC endpoints
    for _, chain := range chains {
        if chain.Name == cctp.Ethereum {
            fmt.Printf("Ethereum RPC: %s\n", chain.RPC)
        }
    }
}

​
Breaking Down the Example

1

Get Default Chains

Start by getting the chains with default RPC endpoints:
chains := cctp.GetChains(false) // false = mainnet
2

Define Custom RPC Map

Create a map with chain names as keys and custom RPC URLs as values:
customRPCs := map[string]string{
    cctp.Ethereum: "https://eth-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
    cctp.Arbitrum: "https://arb-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
    cctp.Base:     "https://base-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
}
Use the chain name constants (e.g., cctp.Ethereum) for IDE autocomplete support and to avoid typos.
3

Apply Overrides

Apply the custom RPC endpoints to your chains:
chains = cctp.ApplyRPCOverrides(chains, customRPCs)
The function returns a new slice and doesn’t mutate the original chains.
4

Use Custom Chains

Now you can use the chains with your custom RPC endpoints:
for _, chain := range chains {
    if chain.Name == cctp.Ethereum {
        fmt.Printf("Ethereum RPC: %s\n", chain.RPC)
    }
}

​
Available Chain Constants

​
Mainnet Chains

cctp.Ethereum
cctp.Avalanche
cctp.OPMainnet
cctp.Arbitrum
cctp.Base
cctp.PolygonPoS
cctp.Unichain
cctp.Linea
cctp.Codex
cctp.Sonic
cctp.WorldChain
cctp.Sei
cctp.XDC
cctp.HyperEVM
cctp.Ink
cctp.Plume

​
Testnet Chains

cctp.EthereumSepolia
cctp.AvalancheFuji
cctp.OPSepolia
cctp.ArbitrumSepolia
cctp.BaseSepolia
cctp.PolygonPoSAmoy
cctp.LineaSepolia
cctp.ArcTestnet
cctp.UnichainSepolia
cctp.CodexTestnet
cctp.SonicTestnet
cctp.WorldChainSepolia
cctp.SeiTestnet
cctp.XDCApothem
cctp.HyperEVMTestnet
cctp.InkTestnet
cctp.PlumeTestnet

​
Important Notes

Chain Name Matching
  • Use chain name constants (e.g., cctp.Ethereum) for IDE autocomplete support
  • You can still use string literals if needed, but they must match exactly (case-sensitive)
  • Empty string overrides are ignored (original RPC is preserved)
  • Non-matching chain names are ignored
ImmutabilityThe original chains slice is not mutated. ApplyRPCOverrides returns a new slice with the overrides applied.

​
Common RPC Providers

customRPCs := map[string]string{
    cctp.Ethereum: "https://eth-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
    cctp.Arbitrum: "https://arb-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
    cctp.Base:     "https://base-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
    cctp.PolygonPoS: "https://polygon-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
}

​
Partial Overrides

You don’t need to override all chains. Only override the ones you need: 
// Only override Ethereum, all other chains use default RPCs
customRPCs := map[string]string{
    cctp.Ethereum: "https://eth-mainnet.g.alchemy.com/v2/YOUR_API_KEY",
}

chains = cctp.ApplyRPCOverrides(chains, customRPCs)

​
Next Steps

Chain Configuration

Learn more about chain configurations

Contract Interactions

Interact with CCTP contracts

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