chore: explain async insert in docs (#969)

README.md

@@ -34,7 +34,7 @@ The client is tested against the currently [supported versions](https://github.c
 * Connection pool
 * Failover and load balancing
 * [Bulk write support](examples/clickhouse_api/batch.go) (for `database/sql` [use](examples/std/batch.go) `begin->prepare->(in loop exec)->commit`)
-* [AsyncInsert](benchmark/v2/write-async/main.go)
+* [AsyncInsert](benchmark/v2/write-async/main.go) (more details in [Async insert](#async-insert) section)
 * Named and numeric placeholders support
 * LZ4/ZSTD compression support
 * External data
@@ -268,6 +268,19 @@ Order is the highest abstraction to the lowest level implementation left to righ
 
 Usage examples for [native API](examples/clickhouse_api/client_info.go) and [database/sql](examples/std/client_info.go)  are provided.
 
+## Async insert
+
+[Asynchronous insert](https://clickhouse.com/docs/en/optimize/asynchronous-inserts#enabling-asynchronous-inserts) is supported via dedicated `InsertAsync` method. This allows to insert data with a non-blocking call.
+Effectively, it controls a `async_insert` setting for the query. 
+
+### Using with batch API
+
+Using native protocol, asynchronous insert does not support batching. It means, only inline query data is supported. Please see an example [here](examples/std/async.go).
+
+HTTP protocol supports batching. It can be enabled by setting `async_insert` when using standard `Prepare` method.
+
+For more details please see [asynchronous inserts](https://clickhouse.com/docs/en/optimize/asynchronous-inserts#enabling-asynchronous-inserts) documentation.
+
 ## Benchmark
 
 | [V1 (READ)](benchmark/v1/read/main.go) | [V2 (READ) std](benchmark/v2/read/main.go) | [V2 (READ) clickhouse API](benchmark/v2/read-native/main.go) |