Help in executing soapui and AWS redshift JDBC connection from docker using lukastosic/docker-soapui

I am trying to run SOAPUI (open source) from docker using lukastosic/docker-soapui and in the SOAPUI I am making a JDBC connection to AWS redshift DB. But unable to run the same via docker and getting the below error message.

java.lang.ClassNotFoundException: com.amazon.redshift.jdbc4.Driver

ERROR [SoapUI] An error occurred [No suitable driver], see error log for details

java.sql.SQLException: No suitable driver

An error occurred [Failed to init connection for driver [com.amazon.redshift.jdbc4.Driver], connectionString [jdbc:redshift:XXXX]

Note: I have downloaded and saved the respective AWSRedshift jar file(RedshiftJDBC4-1.2.8.1005) in the bin/ext folder and using the driver as "com.amazon.redshift.jdbc4.Driver" in the docker. When running the same in local PC as normal SOAPUI file it is working fine.