Jenkinsfile passing arguments within a string fails

Using Jenkins
1

Blockquote

            steps {
                sh '''
                    export PATH=/usr/lib/oracle/19.3/client64/bin:$PATH
                    export LD_LIBRARY_PATH=/usr/lib/oracle/19.3/client64/lib
                    export TNS_ADMIN=/usr/lib/oracle/19.3/client64/lib/network/admin

                    sqlplus 'username/password@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myrdsinstance.rds.amazonaws.com)(PORT=1521))(CONNECT_DATA=(SID=ORCL)))' @my_sql_script.sql
                '''
            }

I want to pass the variables in place of username, password, host and port. I put username, host & port within Env block in the top of the jenkinsfile. I retrieve the password dynamically.
I tried “dollar symbol username” or ${username} or env.DB_USER but it takes as is. Any idea?

2

I replaced single quote with double quotes sqlplus “…”
I was able to get the password using dollarpassword in double quotes. I was still not able to pass env variables. I tried ${env[USER]} as well.