Thanks! @kulatamicuda for hint.
I'm using liquibase with sprinboot, I made working using below setup -

1. I have sql in fn_count.sql

   CREATE OR REPLACE FUNCTION totalRecords ()
   RETURNS integer AS $total$
   declare
     total integer;
   BEGIN
      SELECT count(*) into total FROM COMPANY;
      RETURN total;
   END;
   $total$ LANGUAGE plpgsql\
   

2. fn_count.xml - here important part is - endDelimiter="\"

   <?xml version="1.0" encoding="UTF-8"?>
   <databaseChangeLog
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
           xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
            http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.9.xsd">
       <changeSet id="2025050605" author="AUTHOR">
           <sqlFile path="sql-scripts/fn_count.sql"
                    relativeToChangelogFile="true"
                    endDelimiter="\"
                    splitStatements="true"
                    stripComments="true"/>
       </changeSet>
   </databaseChangeLog>
   

3. db.changelog-master.xml

   <?xml version="1.0" encoding="UTF-8"?>
   <databaseChangeLog
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
   xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
            http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.9.xsd">
   
   <include file="fn_count.xml" relativeToChangelogFile="true"/>
   
   </databaseChangeLog>
   

   File structure looks like this -

   src/main/resources/
   ├── db/
   │   ├── changelog/
   │   │   └── fn_count.xml, db.changelog-master.xml
   │   │   └── sql-scripts/
   │   │       └── fn_count.sql