func (r *Client) CreateAnnotation(ctx context.Context, a CreateAnnotationRequest) (StatusMessage, error) {
	var (
		raw  []byte
		resp StatusMessage
		err  error
	)
	if raw, err = json.Marshal(a); err != nil {
		return StatusMessage{}, errors.Wrap(err, "marshal request")
	}
	if raw, _, err = r.post(ctx, "api/annotations", nil, raw); err != nil {
		return StatusMessage{}, errors.Wrap(err, "create annotation")
	}
	if err = json.Unmarshal(raw, &resp); err != nil {
		return StatusMessage{}, errors.Wrap(err, "unmarshal response message")
	}
	return resp, nil
}
https://grafana.com/docs/grafana/latest/http_api/annotations/
CreateAnnotation creates a new annotation from the annotation request
package sdk
import (
	"context"
	"encoding/json"
	"fmt"
	"net/url"
	"strconv"
	"time"
	"github.com/pkg/errors"
)