Everyone thanks for your help 
Got it working!
public async Task Setup()
{
var settings = new DefaultSerializer();
settings.SerializerSettings.Formatting = Formatting.Indented;
settings.SerializerSettings.StringEscapeHandling = StringEscapeHandling.EscapeNonAscii;
settings.SerializerSettings.ContractResolver = new LowercaseContractResolver();
var options = new ClusterOptions
{
UserName = "testing",
Password = "1233456",
Serializer = settings
};
Cluster = await Couchbase.Cluster.ConnectAsync("couchbase://localhost",options);
Bucket = await Cluster.BucketAsync("test");
Collection = Bucket.DefaultCollection();
}
public class LowercaseContractResolver : DefaultContractResolver
{
protected override string ResolvePropertyName(string propertyName)
{
return propertyName.ToLower();
}
}
