postgres index rebuild

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.3/static/routine-reindex.html
Description:

Hi,

As per the doc provided by postgres, for rebuild index we can do
concurrently which doesn't take any lock.
1)create new index concurrently with different name
2)drop old index
3)rename new index with old index name

my question is

I was trying to keep all the queries(create, drop, alter) in a function. And
'll call the function when required.
But i got below error
"CREATE INDEX CONCURRENTLY cannot be executed from a function or
multi-command string"

Please help me on this

Thanks,
jasho