ctx := context.Background()
client, err := bigquery.NewClient(ctx, projectID)
if err != nil {
        return fmt.Errorf("bigquery.NewClient: %v", err)
}
defer client.Close()

rat := big.NewRat(12345, 10e10)
q := client.Query("SELECT @bigval, @array, @struct")
q.Parameters = []bigquery.QueryParameter{
        {
                Value: ScalarQueryParameter{Name: "bigval", Type: "BIGNUMERIC", Value: rat}
        },
        ArrayQueryParameter{Name: "array", Value: []string{"a","b","c"}, Type: ScalarQueryParameter{Type: "STRING"}}.QueryParameter(),
        StructQueryParameter{
	        Name: "val",
	        Value: map[string]ParameterValue{
		        "Timestamp": ScalarQueryParameter{
			        Value: ts,
		        },
		        "BigNumericArray": ArrayQueryParameter{
			        Value: []string{
				        BigNumericString(bigRat),
				        BigNumericString(rat),
			        },
		        },
		        "SubStruct": StructQueryParameter{
			        Value: map[string]ParameterValue{
				        "String": ScalarQueryParameter{
					        Value: "c",
				        },
			        },
		        },
	        },
	        Schema: map[string]ParameterType{
		        "Timestamp": ScalarQueryParameter{
			        Type: "TIMESTAMP",
		        },
		        "BigNumericArray": ArrayQueryParameter{
			        Type: ScalarQueryParameter{
				        Type: "BIGNUMERIC",
			        },
		        },
		        "SubStruct": StructQueryParameter{
			        Schema: map[string]ParameterType{
				        "String": ScalarQueryParameter{
					        Type: "STRING",
				        },
			        },
		        },
	        },
        }.QueryParameter()
}