For Hibernate as JPA provider use
spring.jpa.properties.hibernate.default_schema=dbo
For plain JDBC, add it to your connection string:
jdbc:postgresql://localhost:5432/mydatabase?currentSchema=myschema
Another option is to run the statement set schema 'dbo' early in each query object. (Yuck!)
BTW your
spring.datasource.schema=dbo
is probably mistake as this property specifies name of the sql file that contains your schema (CREATE/ALTER statements)