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This guide provides instructions for migrating to a new version of ibc-go. Note: ibc-go supports golang semantic versioning and therefore all imports must be updated on major version releases. Diff examples are shown after the list of overall changes:
  • Chains will need to remove the ParamSubspace arg from all calls to Keeper constructors
  app.IBCKeeper = ibckeeper.NewKeeper(
    appCodec,
    runtime.NewKVStoreService(keys[ibcexported.StoreKey]),
-   app.GetSubspace(ibcexported.ModuleName),
    app.UpgradeKeeper,
    authtypes.NewModuleAddress(govtypes.ModuleName).String(),
  )
The transfer module, the packet forward middleware, and the rate limiting middleware support custom address codecs. This feature is primarily added to support Cosmos EVM for IBC transfers. In a standard Cosmos SDK app, they are wired as follows: 
  app.TransferKeeper = ibctransferkeeper.NewKeeper(
    appCodec,
+    app.AccountKeeper.AddressCodec(),
    runtime.NewKVStoreService(keys[ibctransfertypes.StoreKey]),
    app.IBCKeeper.ChannelKeeper,
    app.MsgServiceRouter(),
    app.AccountKeeper, app.BankKeeper,
    authtypes.NewModuleAddress(govtypes.ModuleName).String(),
  )

  app.RateLimitKeeper = ratelimitkeeper.NewKeeper(
    appCodec,
+    app.AccountKeeper.AddressCodec(),
    runtime.NewKVStoreService(keys[ratelimittypes.StoreKey]),
    app.IBCKeeper.ChannelKeeper,
    app.IBCKeeper.ClientKeeper,
    app.BankKeeper,
    authtypes.NewModuleAddress(govtypes.ModuleName).String()
  )

  app.PFMKeeper = packetforwardkeeper.NewKeeper(
    appCodec,
+    app.AccountKeeper.AddressCodec(),
    runtime.NewKVStoreService(keys[packetforwardtypes.StoreKey]),
    app.TransferKeeper,
    app.IBCKeeper.ChannelKeeper,
    app.BankKeeper,
    authtypes.NewModuleAddress(govtypes.ModuleName).String()
  )

​
ICS27-GMP

ICS27 General Message Passing (GMP) has been added as a supported IBC application of ibc-go. It has no parameters.

​
Add StoreUpgrades for ICS27-GMP module

For ICS27-GMP it is also necessary to manually add store upgrades for the new GMP module and then configure the store loader to apply those upgrades in app.go: 
if upgradeInfo.Name == "v11" && !app.UpgradeKeeper.IsSkipHeight(upgradeInfo.Height) {
  storeUpgrades := store.StoreUpgrades{
    Added: []string{gmptypes.StoreKey},
  }

  app.SetStoreLoader(upgradetypes.UpgradeStoreLoader(upgradeInfo.Height, &storeUpgrades))
}
This ensures that the new module’s stores are added to the multistore before the migrations begin. If a chain chooses not to integrate the GMP module, it does not need to add the GMP key to the Added field.