main2.go

package main

import (
    "context"
    "fmt"

    "google.golang.org/grpc"
    "google.golang.org/grpc/metadata"

    "github.com/cosmos/cosmos-sdk/codec"
    sdk "github.com/cosmos/cosmos-sdk/types"
    grpctypes "github.com/cosmos/cosmos-sdk/types/grpc"
    banktypes "github.com/cosmos/cosmos-sdk/x/bank/types"
)

func queryState() error {
    myAddress, err := sdk.AccAddressFromBech32("cosmos1yerherx4d43gj5wa3zl5vflj9d4pln42n7kuzu") // the my_validator or recipient address.
    if err != nil {
        return err
    }

    // Create a connection to the gRPC server.
    grpcConn, err := grpc.Dial(
        "127.0.0.1:9090",    // your gRPC server address.
        grpc.WithInsecure(), // The Cosmos SDK doesn't support any transport security mechanism.
        // This instantiates a general gRPC codec which handles proto bytes. We pass in a nil interface registry
        // if the request/response types contain interface instead of 'nil' you should pass the application specific codec.
        grpc.WithDefaultCallOptions(grpc.ForceCodec(codec.NewProtoCodec(nil).GRPCCodec())),
    )
    if err != nil {
        return err
    }
    defer grpcConn.Close()

    // This creates a gRPC client to query the x/bank service.
    bankClient := banktypes.NewQueryClient(grpcConn)

    var header metadata.MD
    _, err = bankClient.Balance(
        metadata.AppendToOutgoingContext(context.Background(), grpctypes.GRPCBlockHeightHeader, "12"), // Add metadata to request
        &banktypes.QueryBalanceRequest{Address: myAddress.String(), Denom: "stake"},
        grpc.Header(&header), // Retrieve header from response
    )
    if err != nil {
        return err
    }
    blockHeight := header.Get(grpctypes.GRPCBlockHeightHeader)

    fmt.Println(blockHeight) // Prints the block height (12)

    return nil
}

func main() {
    if err := queryState(); err != nil {
        panic(err)
    }
}