return value for counter

Dockerfile

@@ -1,10 +1,11 @@
-FROM solanalabs/rust:1.73.0 AS builder
-RUN rustup toolchain install nightly
-RUN rustup component add clippy --toolchain nightly
+FROM solanalabs/rust:1.75.0 AS builder
+RUN rustup toolchain install 1.75.0
+RUN rustup component add clippy --toolchain 1.75.0
 WORKDIR /opt
 RUN sh -c "$(curl -sSfL https://release.solana.com/beta/install)" && \
     /root/.local/share/solana/install/active_release/bin/sdk/sbf/scripts/install.sh
 ENV PATH=/root/.local/share/solana/install/active_release/bin:/usr/local/cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+RUN solana-install init 1.18.14
 RUN rustup update
 
 COPY . /opt
@@ -25,4 +26,4 @@ FROM ubuntu:20.04
 COPY --from=builder /opt/test-invoke-program/neon-test-invoke-program.sh /opt/deploy/test_invoke_program/
 COPY --from=builder /root/.local/share/solana/install/active_release/bin/solana /opt/solana/bin/
 COPY --from=builder /root/.local/share/solana/install/active_release/bin/solana-keygen /opt/solana/bin/
-COPY --from=builder /opt/deploy /opt/deploy
+COPY --from=builder /opt/deploy /opt/deploy

counter/src/lib.rs

@@ -6,6 +6,7 @@ use solana_program::{
     msg,
     program_error::ProgramError,
     pubkey::Pubkey,
+    program::set_return_data
 };
 
 mod state;
@@ -31,7 +32,7 @@ pub fn process_instruction(
             process_increment_counter(accounts, instruction_data_inner)?;
         }
         _ => {
-            msg!("Error: unknown instruction {}", instruction_discriminant[0])
+            msg!("Error: unknown instruction {}", instruction_discriminant[0]);
 
         }
     }
@@ -53,7 +54,7 @@ pub fn process_increment_counter(
     let mut counter = Counter::try_from_slice(&counter_account.try_borrow_mut_data()?)?;
     counter.count += 1;
     counter.serialize(&mut *counter_account.data.borrow_mut())?;
-
+    set_return_data(&counter.count.to_le_bytes());
     msg!("Counter state incremented to {:?}", counter.count);
     Ok(())
 }