func (cli *Client) ContainerExecAttach(ctx context.Context, execID string, config types.ExecConfig) (types.HijackedResponse, error) {
	headers := map[string][]string{"Content-Type": {"application/json"}}
	return cli.postHijacked(ctx, "/exec/"+execID+"/start", nil, config, headers)
}
ContainerExecAttach attaches a connection to an exec process in the server.
It returns a types.HijackedConnection with the hijacked connection
and the a reader to get output. It's up to the called to close
the hijacked connection by calling types.HijackedResponse.Close.
package client
import (
	"encoding/json"
	"github.com/docker/docker/api/types"
	"golang.org/x/net/context"
)
func (cli *Client) ContainerExecCreate(ctx context.Context, container string, config types.ExecConfig) (types.IDResponse, error) {
	var response types.IDResponse
	if err := cli.NewVersionError("1.25", "env"); len(config.Env) != 0 && err != nil {
		return response, err
	}
	resp, err := cli.post(ctx, "/containers/"+container+"/exec", nil, config, nil)
	if err != nil {
		return response, err
	}
	err = json.NewDecoder(resp.body).Decode(&response)
	ensureReaderClosed(resp)
	return response, err
}
func (cli *Client) ContainerExecStart(ctx context.Context, execID string, config types.ExecStartCheck) error {
	resp, err := cli.post(ctx, "/exec/"+execID+"/start", nil, config, nil)
	ensureReaderClosed(resp)
	return err
}