go-jira | Go client library for Atlassian Jira | REST library

I try to get the date (2020-03-09) from "2020-03-09T08:09:40.000+0000" with this template line:

... [Ticket:{{- .key -}}:{{ .fields.resolution.name }}] starts {{ slice .fields.created 0 10 }} and ends {{ slice .fields.resolutiondate 0 10 }} ...

--> Invalid Usage: template: gojira:7:62: executing "gojira" at : error calling slice: list should be type of slice or array but string

Documentations says:

slice
slice returns the result of slicing its first argument by the remaining arguments. Thus "slice x 1 2" is, in Go syntax, x[1:2], while "slice x" is x[:], "slice x 1" is x[1:], and "slice x 1 2 3" is x[1:2:3]. The first argument must be a string, slice, or array.

Here the complete template I use with go-jira: